Add live trace read support to lttv base library and to command line modules

Change process_traceset_middle to handle live traces
Add lttv_process_trace_update to manage trace update
Add parameter to batchanalysis to indicate a live trace and its update
period.

When activating the live option of the batchAnalysis module, the trace
processing will loop. In each loop, it will wait for the specified
period, update the trace and then read the added events.

Signed-off-by: Yannick Brosseau <yannick.brosseau@gmail.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>